"You have nothing to be sorry about."
this causes toriel to pause, expression softening to one mildly disarmed. toriel lets out a soft breath, surprised by Frisk's own kindness, their own strength they carry. but it wasn't surprising either at the same time. this was frisk, her determined child.
"oh my child, i wish it were so simple like that," toriel says gently. "even if you say it, and truly believe it, it is something i feel. something i carry. "
this guilt and sadness of hers. toriel wears it like a shawl. some days it was better than others. she supposes frisk was able to sense it today, and this has her feel a pull of guilt as well. she was the adult, the mother. frisk needn't worry.
"guilt is a heavy thing, dear one. so is sadness. it is all part of life. i have made many mistakes as a mother, --perhaps i shall make many more--but all i can do is try and try again. that, too, is part of life."
toriel reaches for frisk, giving their small hand a gentle squeeze. warm, comforting.
"but this is not your burden, my child. nor your worries. its all part of an old woman's past." toriel offers frisk a faint smile.
"you always did have a strong heart, you know. you try every day, and it makes you strong.
thank you, for being you and for being my child." that smile turns warmer, more motherly.
"i take care you, you know, frisk," toriel then says more teasingly, trying to ebb away from the emotionally charged conversation. "now speaking of, should we go make pie together, or go outside to enjoy the day?"